Force sensors are typically used in industrial applications to measure applied forces. Force sensors that are suitable for industrial applications such as in robot end-effectors or machining stations are typically based on strain gauges and may be very expensive. While the strain gauge elements themselves may not be expensive, the difficulty of applying and calibrating strain gauges in force sensor applications results in costly devices. These types of force sensors based on conventional strain gauges designed for use in industrial applications, however, are overdesigned for use in measuring human inputs and may be unnecessarily costly. As such, the requirements for these conventional force sensors are unnecessarily stringent for devices used in other applications, such as for interactive human use.
In addition, industrial force sensors are also very rugged and stiff such that applying a force to them causes little or no perceptible deflection. In the case of a conventional strain-gauge sensor, the force to be measured is applied to a very stiff flexure element that causes only an extremely tiny deflection. The flexure may be a rigid beam and to the human eye it may not appear to deflect at all. The strain gauge bonded to the flexure, however, is incredibly sensitive to tiny changes in its length, and although the flexure beam does not bend visibly, the strain gauge nevertheless tells how much deflection has occurred. The amount of deflection is proportional to the force is being applied.
Many different types of industrial machinery and robotic devices are interactively controlled by a human operator. Typically, the human operator manually manipulates a set of controls that indicate to the machine or robotic device the movements desired by the operator. By sensing the operator's manipulation of the controls, the machine determines the operator's intent in moving the device and can implement the desired action.
In general consumer applications such as with computer video games, a handheld joystick is commonly utilized as a user input control device. A joystick typically measures the changes in position of the joystick handle and translates the positional information into a data signal format that can be transmitted to the digital computer. A typical joystick, however, is not rugged or reliable enough to be utilized in an industrial application where the device may become damaged through constant handling and use. The reliability of the control device is also an important factor in an industrial application where a failure of the joystick may result in the loss of control of machinery that may cause an accident and injure nearby personnel or workers.
Needed are human-operated control devices that are rugged enough for industrial applications, yet are not prohibitively expensive.